Correlation of regional cerebral blood flow measured by stable xenon CT and perfusion MRI.

PURPOSE: The purpose of this work was to investigate the validity of perfusion MRI in comparison with stable xenon CT for evaluating regional cerebral blood flow (rCBF). METHOD: The rCBF was measured by xenon CT and perfusion MRI within a 24 h interval in 10 patients (mean +/- SD age 63 +/- 10 years). For perfusion MRI, absolute values of rCBF were calculated based on the indicator dilution theory after injection of 0.1 mmol/kg of Gd-DTPA. Eight to 10 regions of interest (37 mm2) were located in the white and gray matter on the rCBF images for each of the 10 patients. RESULTS: The mean +/- SD values of rCBF in gray matter were 48.5 +/- 14.1 ml/100 g/min measured by xenon CT and 52.2 +/- 16.4 ml/100 g/min measured by perfusion MRI. In the white matter, the rCBF was 22.6 +/- 9.1 ml/100 g/min by xenon CT and 27.4 +/- 6.8 ml/100 g/min by perfusion MRI. There was a good correlation of rCBF values between perfusion MRI and xenon CT (Pearson correlation coefficient 0.83; p < 0.0001). CONCLUSION: Comparable to xenon CT, perfusion MRI provides relatively high resolution, quantitative local rCBF information coupled to MR anatomy.

Changes of cerebral perfusion after osmotherapy in acute cerebral edema assessed with perfusion weighted MRI.

Perfusion is thought to be impaired in brain edema due to reduced perfusion pressure. Brain edema therapy is assumed to improve perfusion. We assessed regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV) and mean transit time of blood (MTT) using perfusion-weighted magnetic resonance imaging (MRI) in 15 patients showing acute local brain edema due to infarction or intracerebral hematoma. Patients were treated by intravenous infusion of 125 ml 40% sorbitol over 10 min. rCBF, rCBV and MTT in the edematous region were measured before and 30 min after treatment. Before treatment rCBF (46.5 +/- 12.1 vs. 42.9 +/- 10.5 ml 100 g-1 min-1), MTT (4.7 +/- 1.9 vs. 4.0 +/- 1.7 s) and rCBV (5.4 +/- 1.7 vs. 4.7 +/- 1.1 ml 100 g-1) were significantly (p < 0.05) increased in the edematous region compared to the contralateral side. After treatment no significant differences could be found. We interpret the elevation of MTT and rCBV in the edema as signs of an autoregulative compensation of an impaired perfusion. rCBF is even over-compensated. After brain edema therapy perfusion seems normalised. This new MRI method appears as useful for measuring therapeutic effects on cerebral perfusion.

Influence of the angiographic internal carotid artery stenosis assessment method on indicating carotid surgery.

BACKGROUND: To estimate the influence of different kinds of angiographic internal carotid artery (ICA) stenosis assessment methods on clinical decision making on carotid surgery. METHOD: One hundred angiographically proven ICA lesions in 65 patients (54 men, 11 women, mean age +/- SD, 64 +/- 8 years) were evaluated by simultaneous biplane angiography. The angiograms were analyzed using three kinds of linear diameter reduction methods [North American (NASCET), and European (ECST) carotid surgery trial method, common carotid artery method (CC)], and five area reduction methods reflecting more accurately the anatomical degree of stenosis [squared NASCET, ECST and CC (N2, E2, CC2), combined stenosis estimation of two projections (NASCET-bi, ECST-bi)]. All lesions were additionally evaluated by continuous wave (cw-)Doppler ultrasound prior to angiography. Between method agreement on classifying the lesions into stenosis < 70% and into stenosis > or = 70% was calculated by means of kappa statistic. RESULTS: The degree of stenosis (median and inter-quartile range) ranged between 65% (38-82) by means of NASCET and 91% (87-93) by means of CC2. Thirty-seven ICA stenoses would have been operated on using NASCET, but 82 using CC2. Between method agreement on assessing high grade ICA stenosis ranged from poor (kappa value 0.17 for the pair NASCET/CC2) to excellent (kappa value 0.92 for the pair N2/NASCET-bi). Cw-Doppler ultrasound showed a good agreement (kappa value 0.72-0.80) with all angiographic methods using an area reduction formula apart from CC2. The agreement was moderate between cw-Doppler and NASCET and ECST, respectively. CONCLUSION: The clinical decision to operate on an ICA stenosis will strongly be influenced by the angiographic method used. Because reliable clinical data exist only for the NASCET and ECST method these two angiographic stenosis assessment method should be used for clinical decision making.

Stereotactic neurosurgery planning with 3-D spiral CT-angiography.

OBJECTIVE: To assess the feasibility and value of spiral CT angiography of the brain vessels for the planning of neurosurgical stereotactic interventions. MATERIAL AND METHODS: Fourty-two patients harboring cerebral lesions underwent spiral CT angiography prior to stereotactic biopsy. Thin spiral CT slices with a collimator slice thickness of 1 mm and a pitch of 1 were used. Multiplanar reconstructions and maximum intensity projections (MIP) were obtained as well as 3-D tissue definition. RESULTS: There was a sufficient visualization of vessels and of their relationship to the lesion. Tumor neovascularization was clearly demonstrated. Arteries could be shown separately. Stereotactic coordinates of targets were chosen at a safe distance from the vessels and the simulation of tarjectories using the cine loop was made possible. In three cases the presence of a pathological vascularization warned against a stereotactic biopsy. CONCLUSION: Spiral CT angiography seems to yield enough topographical information for the accurate planning of stereotactic surgery for brain lesions. CT angiography with the helical technique is rapid and less invasive than digital subtraction angiography.

[Diffusion-weighted magnetic resonance imaging in the diagnosis of cerebral infarct]. / Diffusionsgewichtete Kernspintomographie zum Nachweis zerebraler Infarkte.

Forty-one patients demonstrating clinical symptoms for cerebral infarction were investigated by magnetic resonance imaging with diffusion-weighted echo-planar imaging (DWI) and T2-weighted imaging (T2WI). In 8 patients only DWI showed the cerebral lesions clearly. One patient with positive DWI and T2WI suffered from HSV encephalitis. DWI is superior to T2WI in assessment of small cortical infarcts and cerebral infarction in patients with preexisting vascular lesions. DWI is not specific, so other causes like cerebral hematoma and encephalitis have to be considered.

[Perfusion-MRI in cerebral infarct]. / MR-Perfusionsuntersuchung beim Hirninfarkt.

PURPOSE: To investigate the hemodynamic changes in patients with acute cerebral stroke by perfusion MRI. MATERIAL AND METHODS: In 12 patients with acute stroke in the territory of the middle cerebral artery, perfusion MRI was performed. Peak time, mean transit time, regional cerebral blood volume and regional cerebral blood flow were calculated in the infarction, the peri-infarction area and the contralateral hemisphere. RESULTS: In the infarction the mean blood flow was 29 ml/100 g/min, compared to about 40 ml/100 g/min in the peri-infarction area and the contralateral hemisphere. In two patients increased cortical blood flow was found in the infarction due to luxury perfusion. The cerebral blood volume was reduced in the infarction, but significantly increased, to 7.3 ml/100 g, in the peri-infarction tissue. CONCLUSION: Perfusion MRI allows one to differentiate various patterns of perfusion disorders in patients with acute cerebral stroke. The resulting data may be helpful in describing the pathophysiologic mechanisms of compensation.

Patient doses from standard and spiral CT of the head using a fast twin-beam system.

Investigations were carried out on a novel type of CT scanner, the Elscint CT-Twin, for comparison and optimization of the patient dose caused by standard and spiral CT of the head. For selected CT parameters, organ doses of the Alderson head phantom were measured with thermoluminescent dosemeters. Organ doses were also calculated using the normalized computed tomography dose index (CTDIn) combined with organ dose conversion factors. Then effective doses were deduced. For standard and spiral head CT examinations brain, red bone marrow and bone surface receive the main contributions to effective dose. This amounts to 0.9 and 0.8 mSv for routine standard and spiral CT, respectively, if the combination "dual-slice" mode, 250 mAs per rotation, 5 mm nominal slice width and a packing factor of 1.0, is applied. In clinical practice, for spiral CT head examinations the effective dose has been reduced to 0.7 mSv while guaranteeing adequate image quality, as assessed by determination of low and high contrast resolution. The effective dose values obtained are in the lower part of the range of values published in the literature. The dose determinations showed that, from the aspect of radiation protection of the patient, CT examinations with nominal slice widths between 0.5 and 1 mm as well as packing factors greater than 1.0 should be restricted to really necessary cases.

[Value of CT-angiography in diagnosis of cerebral sinus and venous thromboses]. / Stellenwert der CT-Angiographie in der Diagnostik von zerebralen Sinus-und Venenthrombosen.

Dural sinus thrombosis is not uncommon. Due to the nonspecific symptomatology, as well as the manifold etiology, clinical diagnosis may be difficult. In these cases imaging procedures are frequently crucial in deciding how to proceed and how to treat. The aim of our study was to evaluate the diagnostic utility of helical CT in the detection of dural sinus thrombosis. In 20 patients with clinically suspected thrombosis CT angiography was performed. In 6 patients dural sinus thrombosis was diagnosed. In order to acquire also arterial vessels, a short delay of about 22 s after the onset of the application of contrast medium was selected. By this method we found an occlusion of the MCA in two patients with clinically suspected sinus thrombosis. In all patients the transverse slices and the multiplanar reconstructions showed filling defects or an "empty delta" sign. With irregular outlines the thrombus could be depicted over the complete course of the sinus. The MIP reconstructions were particularly helpful in the evaluation of the vessel anatomy and the pathological collateral venous drainage. In three patients MR angiograms were available for comparison. The smaller veins, such as the v. vermis inferior, were less clearly depicted than in CT angiography. CT angiography is a fast and reliable method to exclude or verify a sinus thrombosis. It can be performed immediately after non-enhanced CT. According to our present experience CT angiography is sufficient for the diagnosis of a sinus thrombosis.

[CT-angiography in planning stereotaxic biopsies]. / CT-Angiographie in der Planung stereotaktischer Biopsien.

Twenty-one patients referred for stereotactic biopsy were studied by CT angiography. Helical CT with 1 mm collimation was obtained (pitch of 1:1). Multiplanar reconstructions were performed; maximum intensity projections and shaded-surface displays were generated by connectivity-based editing tools. The visualization of cerebral vessels was excellent. No further conventional angiography was needed. Improved information was obtained about localization of the intracranial lesion and its relationship to neighboring vessels. No bleeding complications were detected by CT after stereotactic biopsy.

[Angiographic quantification of stenoses of the internal carotid artery]. / Zur angiographischen Quantifizierung von Stenosen der Arteria carotis interna.

BACKGROUND AND PURPOSE: The method of measuring cartid stenosis is under discussion since different methods of quantifying carotid stenosis were used in the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Stenosis Trial (ECST). METHODS: Angiograms from 80 patients (105 cases of stenosis of the internal carotid artery), performed in a simultaneous biplanar manner, were retrospectively analyzed using the NASCET, the ECST method and a method based on measurement of the common carotid (CC) artery lumen diameter. Each linear measurement was converted into the ¿squared¿ method (NASCET2, ECST2, CC2). The linear NASCET and ECST measurements of both views (stenosis 1, stenosis 2) were used to calculate the biplanar stenosis according to the formula: stenosis = stenosis 1 + stenosis 2 - stenosis 1 * stenosis 2, and termed ¿local stenosis ECST-bi¿ and ¿distal related stenosis NASCET-bi¿ Furthermore each stenosis was approximated by two neuroradiologists. RESULTS: Direct visualization proved agreement with measured local stenosis ECST-bi. Squared methods correlated exactly with linear measurements (Spearmancorrelation), thus providing no further data. Biplanar calculation caused considerable change in the order of the stenosis. The different results of the local stenosis ECST-bi and the distal related stenosis NASCET-bi are not contradictory, but complementary. CONCLUSIONS: Direct visualization should be replaced by measurement of the local stenosis ECST-bi. Biplanar calculation seems to give a better estimate of the degree of the stenosis, causing questions since the results of ECST and NASCET cannot be applied.